1. Field of the Invention
The present invention relates to a multi-resolution printing device, and more particularly, to a printing device only processing one base-frequency clock to allow documents with different resolutions be printed out with their original sizes.
2. Description of Prior Arts
Along with the increasing development of small office home office (SOHO), in order to spend less time on operating different office equipments for different requirements, more and more SOHOs and small enterprises choose to adopt multi-function printers (MFPs), almost integrating every office machine function such as copying, faxing, scanning, and printing together. By this way, a small office company is able to run smoothly even with only one MFP equipped, and thus, to save some time waste.
Generally, when printing, the required resolution is 600 dpi of the imperial system. When faxing, the required resolution is only about 203 dpi of the metric system. Therefore, the MFP needs two clocks of different frequencies to provide different resolutions applicable to imperial or metric system.
As shown in FIG. 1 of a control circuit block diagram, the control circuit for providing different resolutions includes a first base-frequency clock generator 1a, a second base-frequency clock generator 1axe2x80x2, a first frequency divider 2a, a second frequency divider 2axe2x80x2, and an external selector 3a. 
The first base-frequency clock generator 1a can generate a base-frequency clock for a resolution of M times of 600 dpi. The second base-frequency clock generator 1axe2x80x2 can generates a base-frequency clock for a resolution of N times of 203 dpi. The first frequency divider 2a, being a frequency divider with a divisor of M, is connected to the first base-frequency clock generator 1a, hence obtaining an output printing clock for 600 dpi resolution. The second frequency divider 2axe2x80x2, being a frequency divider with another divisor of N, is connected to the second base-frequency clock generator 1axe2x80x2, hence obtaining an output printing clock for 203 dpi resolution. The external selector 3a is connected to the first frequency divider 2a and the second frequency divider 2axe2x80x2, and is controlled by the system to selectively output the printing clock for 600 dpi or 203 dpi resolution to a printing engine 4a. In other words, when printing, the external selector 3a selects the printing clock for 600 dpi resolution of the first frequency divider 2a; when faxing, the external selector 3a selects the printing clock for 203 dpi resolution of the second frequency divider 2a. 
However, there are usually not just two printing clocks required for a MFP. When the number of printing clocks increases, it is necessary to increase the number of components like base-frequency clock generators and frequency dividers accordingly. Because the base-frequency clock generators are expensive, the total cost of manufacturing one MFP relatively raises.
The primary object of the present invention is to provide a multi-resolution printing device, which only processes one base-frequency clock to allow documents of different resolutions required to be printed out with their original sizes. Sizes of the printing dot are variable in this invention, accordingly changing corresponding resolutions to allow documents of different resolutions to be printed with their original sizes.
Another object of the present invention is to provide a multi-resolution printing device, with the simplified circuit to save the hardware cost.
To achieve the above objects, the present invention provides a multi-resolution printing device, which includes a base-frequency clock generator and a control unit. The base-frequency clock generator is used to generate only one base-frequency clock. The control unit is connected to the base-frequency clock generator, and is used to process the base-frequency clock to output several printing clocks with different resolutions to a printing engine.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which: